1. Field of the Invention
The present invention relates to a structure comprising high-frequency components, for example a protection structure.
2. Discussion of the Related Art
Generally, electronic components are formed either in a solid substrate semiconductor wafer, or in a semiconductor-on-insulator (SOI) layer.
FIG. 1 shows the upper portion of a doped solid substrate 1 of a first conductivity type, for example, P, in which are formed several doped wells 3 of a second conductivity type, for example N. High-frequency electronic components can then be formed in wells 3. The isolation between wells 3 results from an appropriate biasing of the PN junctions between wells 3 and substrate 1. The capacitances between a well 3 and substrate 1 and between two neighboring wells 3 are often non-negligible as compared with the specific capacitances of the components formed in wells 3 and this is a problem, especially in the field of high-frequency components.
FIG. 2 shows an example of an SOI type structure. This structure comprises, on a semiconductor support 5, a thin layer of a semiconductor substrate with an interposed silicon oxide layer 7. Semiconductor wells 9, in which are formed electronic components, are formed side by side in the substrate. The free space between the wells is occupied by an insulator, for example, silicon oxide 11. The silicon oxide of layer 7, as for itself, enables insulating the electronic components in the vertical direction. This structure has the advantage over the structure of FIG. 1 of decreasing the values of the stray capacitances between neighboring components. However, these capacitances are not negligible in certain cases, especially at high frequency.